1. Field
The inventive concept relates to a transmission delay measurement and more particularly, to a node unit capable of measuring a delay and a distributed antenna system including the same.
2. Description of Related Art
Delay equalization processing in a distributed remote device (e.g., a remote unit in a distributed antenna system, a remote radio head (RRH) in a base station distributed system, or the like) is required in a distributed transmission system for mobile communication signals, such as the distributed antenna system or the base station distributed system.
In particular, the delay equalization processing is important in an orthogonal frequency division multiplexing (OFDM)-based signal transmission system such as long term evolution (LTE) or WIBRO. In OFDM-based signals, it is important to maintain orthogonality between carrier wavers for performing a discrete Fourier transform (DFT) operation in a cell overlapping region. This is because, in order to maintain the orthogonality, it is required to provide mobile communication services through distributed remote devices at the same time.
Therefore, in a signal distributed transmission system, the accurate measurement of a transmission delay is required as a precondition of the delay equalization processing for improving the quality of mobile communication services.